Patients with systemic lupus erythematosus have been found to have disturbances of cell-mediated immune responses. Alterations of B and T lymphocytes as well as monocyte function, natural killer cell and interferon responses have been observed both in patients with SLE and certain of their relatives. The major goal of these studies is to further characterize the types of immunological disturbances in SLE and to elucidate the mechanisms which lead to alterations of immune regulation and are responsible for the pathogenesis of this disease. The ability of immunosuppressive drugs to alter cell mediated immune function and possibly to re-establish more nearly normal immunoregulation is being actively studied.